When getting back into his saddle after visiting his mother and sister, Octavian's horse is clearly fitted with stirrups. In Roman era saddles the rider had to depend on squeezing two horns in the saddle between his thighs. Stirrups were not used in and were only generally adopted in Europe. No full example of a Roman saddle remains and all those used are reconstructions at best from recovered fragments.
When Agrippa, Octavius and Maecenas are hiding in a fish cart, someone taps the side on the cart so they know when to climb out but Agrippa tells Maecenas to hurry before they're seen. As they are climbing out, two crew members can be seen holding the sides still to stop the three men falling over.